Pneumatic liquid dispensers are known as mechanisms for applying a liquid onto an application surface, such as the surface of a semiconductor substrate, in a dotted or linear form. In liquid dispensers, a pump or other pressurizing element is used to pressurize a liquid, and the liquid is dispensed from a nozzle having a prescribed diameter and applied to an application surface. The inventors proposed, in Patent Document 1, a microvolume-liquid dispenser with which it is possible to precisely apply droplets present in an amount measured in nanoliters or even picoliters through an inexpensive configuration using, e.g., a nozzle having a very small diameter of 500 μm or less.
In liquid dispensers for applying an application liquid in a small amount or with a very small width, there have been cases in which, when application is started from a standby state or when an application operation is repeatedly performed, the application state or application quantity changes if the time interval of the application operation changes, making it impossible to obtain the same application results. This problem presumably arises because the nozzle tip end dries over time, the fluidity of the application liquid declines (the viscosity thereof rises), and the liquid surface of the application liquid formed in a nozzle tip-end opening is drawn into the nozzle (the liquid surface height changes).
In the prior art, in order to avoid clogging of the nozzle, inferior application, and other such adverse circumstances caused, inter alia, by drying of the application liquid at the nozzle tip end, the nozzle is moved to a prescribed position and an application liquid discharge operation unrelated to the actual application operation is performed in cases when the application standby time is long, the discharge operation being referred to as “wasteful discharging.” In such an operation, wasteful movement of the nozzle increases, and wasteful consumption of application liquid also increases. In addition, the location at which the wasteful discharging is performed is typically set apart from the application position, and it takes time to move the nozzle so as to return from the position at which the wasteful discharging is performed to the application position. When application is performed, inter alia, using a solution that has excellent drying properties, drying of the solution at the nozzle tip end is promoted while the nozzle is returned to the application position. Therefore, there are cases where the desired application cannot be performed, irrespective of whether wasteful discharging is performed.
In the application film formation device disclosed in Patent Document 2, the liquid surface at the tip end of the nozzle is drawn upward into the nozzle during standby, preventing drying of the application liquid at the nozzle tip end. Prior to application, the liquid surface of the application liquid that was drawn upward into the nozzle is drawn back down toward the nozzle-tip-end side, preventing a deficit in the amount of application liquid discharged from the nozzle during the first application after standby and thus preventing unevenness in application.